Tunable magnetron



March 18, 1952 s. SONKIN 2,589,835

TUNABLE MAGNETRON Filed 001;. 19, 1945 3 SheetQ-Sheet 1 FIG. 1. AMPLIFIER INVENTOR.

SIMON SONKIN ATTORNEY S. SONKIN TUNABLE MAGNETRON March 18, 1952 3 Sheets-Sheet 2 Filed Oct. 19, 1945 AMPIFIER 4.!

FIG. 7.

INVENTOR. SIMON SON KIN ATTO R N EY March 18, 1952 s. SONKIN 2,589,885

TUNABLE MAGNETRON Filed (Jet. 19, 1945 3 Sheets-Sheet 3 FIG. 8.

IOOI FIG. 10.

INVENTOR.

SIMON SONKIN flaw 4.. Q/lu ATTO R NEY Patented Mar. 18, 1952 UNITED TUNABLE MAGNETRON Simon Sonkin, New York, N. Y., assignor to the United States of America as represented by the Secretary of War Application October 19, 1945, Serial No. 623,423

11 Claims.

- The-invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to ultra-high frequency generators of magnetron type in which ultrahigh frequency oscillations are generated by a plurality of resonators set into oscillations by high velocity electrons moving along curvilinear or orbital paths because of the joint action of the electrostatic and electromagnetic fields.

It is an object of this invention to provide a means for adjusting the frequency of oscillation of a magnetron.

An additional object of this invention is to provide instrumentalities which, when connected to a source of varying current such as alternating current, audio, or video signal, may be used for frequency modulating the output of the magnetron.

It is another object of this invention to provide a tuning mechanism for a magnetron in which the tuning mechanism is located within one of the magnetic pole pieces of a magnetron thereby conserving space, using the pole piece as a sturdy housing for the mechanism, and affording convenient manipulation of the tuning member.

Two extensively used forms of ultra-high frequency magnetron oscillators incorporate, in one instance the so-called hole-and-slot anode, and, in the other a vane-type anode with the cathode centrally positioned with respect to the resonators of the anode. In order to separate the modes of vibration in the magnetrons of these types they are ordinarily provided with some sort of strapping. The operating frequency of such plural cavity magnetrons is chiefly determined by the dimensions of the anode, which in turn determine the distributed capacities and inductances of the resonators. When the frequency generated by the magnetrons is especially high the use of strapping becomes quite difiicult because of the small dimensions of the anode, and when this is the case the anode is given the form ofthe so-calledVRising Sun in which the radial dimensions of the radially diverging, cavities or slots have different radial lengths.

ing sun Magnetron"! The separation of the modes of vibration in the anodes of For a more detailed description In the production of plural cavity magnetrons, whether they are of the hole-and-slot, Vane, or the Rising Sun types, it is often difficult to construct the components thereof to dimen sions which generate the precisely desired frequency, this being especially so when the oscillations are of extremely short wave length. Consequently it becomes desirable to have some simple mechanical arrangement for tuning magnetrons after their assembly in order to shift its operating frequency to an exact predetermined desired value. The tuning means permits considerable relaxation of the anode manufacturing tolerances at the machine shops, and is also desirable for field use for obvious tactical reasons, for example, when the oscillator is used with the radar equipment, and there is an ever present possibility of jamming of the specific wave length by hostile transmitters The invention discloses three methods of'tuning magnetrons by means of electromagnetic converters which act to convert controlling currents into variations in the position of tuning instrumentalities. In the first two methods the tuning is accomplished by varying the posotion of 'a washer equipped with a plurality of metallic tuning pins or a tuning metallic washer with the pins placed above the anode in one of the end zones of the magnetron, the position of the washer being adjustable by means of a solenoid and a plunger mounted within the solenoid and connected to the washer. The plunger is either raised or low- .ered in the solenoid, depending upon the current carried by the solenoid winding, and the linear travel of the plunger either raises or lowers the washer with respect to the anode. This varying of the air-gap between the washer and the anode changes the distributed capacitance and inductance of the anode and thus changes the output frequency of the magnetron. If the position of the washer is varied in response to some intelligence signal, the position of the washer with respect to the anode will follow the intelligence signal, which will produce a frequency modulated signal in the output of the magnetron.

In the third embodiment of the invention tuning or frequency modulation of magnetrons out- 'putis obtained by varying the positions of two metallic elements made of copper or copper;-

, plated stainless steel whose shape may best be defined as two split portions of a washer orsemiwashers which are separated from each other and the anode by air-gaps. Each of the semiwashers is placed in the end zone of the magnetronwhere they a P6111 Pi Sus de -re a u h anode by the metallic rods protruding through a pole piece. When current of proper polarity is impressed on the rods and on the semiwashers, the semiwashers either approach or recede radially from the center of the anode structure because of the interaction between the permanent magnetic field and the electromagnetic field produced by the currents'carried by "the semiwashers. When the semiwashers either approach or recede from the center of the anode, they vary the distributed inductances and capacitances of the resonators and thus produce a variation inthe frequency generated by the, magnetron.

These and other features of the. invention will be more clearly understood from the following detailed description and the accompanying drawings in which;

Fig. 1 is a vertical cross-sectional view of a tunable magnetron,

.EigHZiS .a horizontal cross-sectional view of the anodeproper taken along line 22. illustrated iniFig. 1,

..Fig.3..illustrates a plan'view of the corrugated springs usedin connection with Fig. 1,

.Fig. 4 illustrates connections'between the mag netron of ,Fig. '1 and asource'of'signals'for frequency. modulating the output ofthe magnetron, 'Fig. '5 is a vertical cross-sectional view "ofa modified tuning arrangement forithei'ma'gnetron,

.Figifi is a vertical 'cross sectional'view :of'still another tuning arrangement for a" magnetron,

.Fig. '7 llllustrates modified connections between the tuning means and a source of signals which produce frequency modulation in the output 'of .theimagnetron of Fig. 6,

IFigs. 8, '9, and .10 illustrate several versions 'of ianapplication of thetuning arrangement. illustratedin'Fig. 6 to a magnetron havingthe'Rising Sun anode.

IRferringLtd'FigJl, it discloses a vertical cross- 'sectionalview of the magnetron with the tuning mechanism mounted in the upper pole piece H! of the magnetron and with the :cathode l:2.being supported by a'(Kovar) tube! 4 mounted in'the opposite polepiece 15. The heater coil of the cathodeis mounted within thecathode l2 and is not visible in the figure. Th heater is'connected toa'heater battery [8 through a centrally mounted and insulated conductor 23 and tube [4. The outer surface of the cathode iscoated in the usual manner with'the 'electron emitting oxides such as barium and strontium oxides. An "anode 22 whose horizontal crosse'sectional view taken alongline'2-2 is illustrated in Fig..2,'is by" the "way of an example a known.hole-and-slotano'de.

'ingrapplication Serial No. 623,422, titled Tunable lvfagrietron'fifiledon October 19, 1945,'now abandoned. Theanod'e ismounte'd ina non-magnetic metallic shell 24 which integrates'the pole pieces '16 and Land the anode 22 intoasingle rigid structure with the pole pieces beingpositioned above and below the anode "and "definingmhe .upper and lower end zones 26 and 28 'of the mag- "netron respectively. The magnetic'field issupplied bya'pairof permanent magnets, one of which, magnet being partially illustrated in Figure 1. The lower'en'dzone-is usedlfor'mounting *aloop 3llwhich is connecte'dtoan outgoing concentric line 32 representing the output circuit of the magnetron. The concentric line may be connected to a broadly tuned wave guide or any other means for utilizing its output in well known manner. The upper end zone includes a fiat washer 34 provided with a plurality of metallic tuning pins 36 made of copper or copper-plated stainless'steel which are primarily. responsible for altering the frequency of the magnetron in the manner fully discussed in my previously mentioned application, Serial No. 623,422, now abanidoned. In Fig. 2, the diameter of the tuning .pins 33 has been illustrated as being considerably .smaller'tthan thediameter of the holes. Whenever maximum obtainable range of tuning or maximum frequency modulation is desired the diameter 'of theiuning pins should be made as large .as possible and only enough clearance provided between the pins and the cavities to prevent flash-overs with the existing ultra high frequency potentials. "Moreover, the pins'should be positionedcoaxially'with'the holes for obtaining themaximum change in frequency per unit length of travel of the pins. The disk issupported'bya plurality of metallic rods and 4| whichare attached'toarod holder 42 made of ferromagnetic "metal placed in a well 44 of'the upper pole piece 19. .The rod holder itself is attached to a red-"46 and a'ferromagnetic solenoid plunger '48. "The plunger is mounted in a non-magneticmetallic cylinder 56 which, together with plate 52, acts as the'upper vacuum seal of the magnetronjthe seal being accomplished by a'solderedjoint 53 between the polepiece and plate 52. coaxially supported within pole piece -|0'by a pair of spaced corrugated springs 54' and 56 which are connected'in'the'center to rod 45 andwhose "outer'en'ds are'connected topole piece 10. "The plan view of'springs 54 and 56 is illustrate'd'in Fig. 3.- The spring is bifurcated and consistsof corrugated elements 300, 302, and 304, the 'centraljunctionportion 306 of 'thethree arms being joined torod 43 by a'soldering joint. The actrugations in springsifiand 56 are'introduced'for making them very flexible so thatthey offer'low resistance to the vertical travel of the structure centering rod 45 within the pole piece. The springsalso hold plunger 48 in the central position within'cylinder 50, the plunger fitting loosely into the cylinder for avoiding the frictional losses between the cylinder and the plunger. Cylinder 5B issurrcunded bya coil 58 whichis connected to a source of potential 60 through 'a' rheostat 62. When the solenoid coil 58 is energized, plunger 48 is drawn up, against theresistance'of springs and 56, to the'position corresponding tothe'lea'st reluctance path'for the flux producedtby'thesole- 'noid. The plunger is drawn into thesOlenoidLto the extent controlled by ,the magnitude ofthe voltage applied to coil 58 and the resiliency of .the springs. The frequency of the magnetron is varied in accordance with the position Of'thB tuning pins'with respect tothe anode. 'When it "is desirable to "produce a frequencymodulated signal in connection with the "tuning "arrangement: illustrated in'Fig. l, the "solenoid coili.58 is connected to an amplifier 430 and'a microphone 4232, in which case the "position "of "the Fig. 5 discloses a tuning or frequency modulating arrangement for a magnetron in which the tuning is accomplished by means of a metallic washer 500 made of copper or copper-plated steel, the remaining elements in the structure illustrated in Fig. 5 being identical to those illustrated in Fig. 1 and therefore bear the same numerals. Fig. 5 may be superimposed over Fig. 1 for the completion of Fig. 5 by matching the illustrated dotted lines 5-5 and 5A5A illustrated in both figures. The tuning arrangement illustrated in Fig. 5 will produce smaller frequency changes than the one illustrated in Fig. 1 since the pins produce larger changes in the distributed inductances and capacitances of the anode than the disk. For a more detailed description of the functioning of the tuning arrangement illustrated in Fig. 5 reference is made to my co-pending applications on Tunable Magnetron, Serial No. 623,422, filed October 19, 1945, now abandoned, and 'Serial No.

trates a vertical cross-sectional view of an additional modification of the magnetron tuning or frequency modulation arrangement, with some of the elements of the structure foreshortened to illustrate the mechanism in a single drawing. A slot-and-hole magnetron anode 800 is fixed to an outer shell 602. A cathode S04 is centrally mounted in the central opening of the anode in the usual manner, the cathode structure being supported by a lower cathode pole piece 605 in the known manner. The upper tuning pole piece 608 besides being used as a low reluctance path for a permanent magnet 5I0which furnishes the necessary flux for the cathode-anode -space'is also used for supporting the tuning structure of the magnetron. Since the illustrated cross-sectional view bisects the anode, only one half of the tuning structure is visible in the a truding terminals of the rods being connected either to a source of potential 626 through a rheo- Stat 628 or to an amplifier I00 and a microphone I02 illustrated in Fig. '7, which may be connected to Fig. 6 along a dotted line I'I. The two pairs of rods may be connected either in series or in parallel to the source of potential, preferably in a manner which will result in the instantaneous currents in the semiwashers to flow in opposite directions. .The vacuum seal of the magnetron is completed by means of a metallic cylinder 630 and a glass cylinder 632, the metallic cylinder 630 being soldered to the pole piece and the glass cylinder making a glass seal 63% with the metallic cylinder.

Figs; 8, 9,an-d lG,il-lustrate "a plan view of the anode andtuning-semiwashers 800 and 802, 900

and 902, I000 and I002, with respect to the anodes 80I, MI, and IO0I respectively. structure illustrated in these figures is of the Rising Sun type which is disclosed in the copending application of Sidney Millman on Rising;Sun Magnetron," filed March 1, 1946, Serial No."651,3l7. The figures illustrate the two en;

The anode Tit treme possible positions of the tuning semiwashers with respect to the anode. The lower washnating elements of the Rising Sun anode. This change of the positions of the semiwashers with respect to the anode is accomplished by impressing a current of desired magnitude on the metallic semiwashers from a source of potential 625 or microphone I02 illustrated in Figs. 6 and 7 respectively. When current flows through the metallic rods 6I6 and 618, Fig. 6, and semiwasher .6 '2, because of the interaction between the permanent magnetic flux produced by the permanent magnet 6I0 in the end zones of the magnetron and the magnetic field surrounding the semiwashers such as (H2 or any of the semiwashers illustrated in Figs. 8 through 10, these semiwashers are deflected toward or away from the center line of the magnetron as is illustrated in Figs. 8 through 10. When the semiwashers are deflected outwardly and away from the center line of the anode structure as illustratedby the positions of the semiwashers 802, 902, and I 002. the effect of the semiwashers on the distributed inductances and capacitances of the resonating elements of the anode is least and therefore the frequency of the magnetron is determined primarily by the physical dimensions of the anode. When the deflecting forces acting on the semi- "washers are such as to swing both of them simul- While the semiwashers in Figs. 8 through 10 are illustrated so that the right semiwashers are in the extreme outer position while the left semiwashers are in the extreme inner position with respect to the center of the anode structure, the actual operation of semiwashers is such that both of them simultaneously are either in the extreme inner or outer positions. It is obvious that such operation of the semiwashers will produce the desired maximum frequency changes as well as uniform loading and uniform frequency changes Over the entire circumference of the anode, a condition always desirable in any tuning arrangement of the symmetrical anode structures of the magnetrons.

While the invention has been specifically illus trated in connection with the hole-and-slot and Rising Sun types of anodes, it'is to be understood that it is equally applicable to the anodes having other known configuration of the resonating elements, such as vane type anodes, in which case the tuning washers, such as washer 500, may be of plain circular type and the semiwashers also of the plain circular type, such as those illustrated. in Figs. 6, 8, and 9. In Fig. 10 the semiwashers are provided withcircular'cut-outs i004 'for reducing the local .resonances in the. semithe apparatus shown .may be made within the scope of the following claims.

I claim:

1. A magnetron having a multi-resonator anode, pole pieces mounted in spaced relationship with respect to said anodes thereby defining the end spaces of said magnetron, electrically conductive tuning means located within one of the end spaces in spaced relationship with respect to said anode and the adjacent pole piece, movable conductive supporting means for said tuning means mounted within one of said pole pieces,

'said tuning means being electromagnetically adjustable with respect to said anode, the position of said tuning means controlling the operating frequency of the resonators of said anode.

2. A magnetron as defined in claim 1 in which said tuning means is a metallic washer mounted coaxially with respect to said anode, the radial dimension of said washer being proportioned so as to produce a predominantly inductive tuning of said anode. I 8. A magnetron as defined in claim 1' in which saidtuning means includes a plurality of metallic tuning pins insertable into the resonating cavities of said anode, the position of said metallic pins when inserted-being in the" inductive region of said resonators whereby the tuning of said anode is accomplished by altering primarily the distributed inductances of said resonators.

4. An ultra-high frequency magnetron including a cathode, a multi-resonator anode coaxially mounted with respect to said cathode, first and second pole pieces mounted in spaced relationship with respect to said anode, said first pole piece and said anode defining an end space, metallic instrumentalities located within said end space, movable conductive supporting means for said instrumentalities mounted within said first pole piece, and means, including an electromagnetic converter for altering the position of said supporting means and said instrumentalities with respect to said first pole piece for varying the operating frequency of said magnetron.

5. An ultra-high frequency magnetron having a multi-resonator anode, pole pieces mounted in spaced relationship with respect to said anode thereby defining the end spaces of said magnetron, tuning instrumentalities mounted within one of the end spaces in spaced relationship with respect to said anode and the adjacent pole piece, and electromechanical means for adjusting the position of said tuning instrumentalities with respect to said anode, said means including a solenoid for altering position of said tuning instrumentalities with respect to said anode whereby the operating frequency of the resonators of said anode is governed by the action of said solenoid.

6. An ultra-high frequency magnetron having a multi-resonator anode, first and second pole pieces respectively above and below the circumferential surfaces of said anode, end spaces between said pole pieces and said surfaces, a metallic element positioned in spaced relationship with respect to the adjacent circumferential surface of said anode and said first pole piece in the and space defined by said first pole'piece, a solenoid coil, a plunger within said solenoid, and mechanical connections between said-plunger and said element, said plunger varying the position of said 8 element with respect to said anode in response to the electromagnetic field of said coil whereby the operating frequency of the resonators of said anode is governed by the electromagnetic field produced by said coil.

'7. An ultra-high frequency magnetron as defined in claim 6 in which said anode is a holeand-slot anode, and said element is a Washer having a radial dimension substantially equal to the combined radial dimension of said slot and said hole.

8. An ultra-high frequency magnetron as dc.- fined in claim'fi in which said element is a metallic Washer and a plurality of metallic tuning pins connected to said washer.

9. An ultra-high frequency magnetron including a cathode ,an anode with a plurality of resonators, said cathode and said anode having a common longitudinal axis, first and second pole pieces mounted in spaced relationship with respect to the circumferential surfaces of said anode, two semiwashers, each of said semiwashers being mounted on two metallic rods in spaced relationship with respect to each other, said cathode and with the adjacent circumferential surface of said anode and said first pole piece, metallic and glass members mounted on the first pole piece and forming a part of a vacuum seal of said magnetron, said ro-ds protruding through said glass member, and a gas-tight seal between said glass member and said rods.

10. An ultra high frequency magnetron including a cathode, an anode with a plurality of resonators, said cathode and said anode having a common longitudinal axis, electrodynamic means for reacting with the fields in said resonators to modify said fields, comprising a plurality of metallic washer segments held in spaced relationship with respect to each other, said cathode and one of the circumferential surfaces of said anode.

11. An ultra-high frequency magnetron including a cathode, an anode with a plurality of resonators, an evacuated chamber enclosing said cathode, anode and resonators, said cathode and said anode having a common longitudinal axis, a tuning instrumentality mounted adjacent to said anode resonators, electrodynamic means for altering the position of said instrumentality relative to said resonators, resilient supporting means for said tuning instrumentality located within said chamber and intermediate said electrodynamic means and said instrumentality, for varying the characteristics of the generated wave in accordance with variations in the position of said instrumentality with respect to said resonator.

SIMON SONKIN.

REFERENCES CITED Ihe following references are of record in the file of this patent:

UNITED STATES PATENTS 

